Fats contribute from 30% to 40% of the total calories consumed by most Americans. One of the most common nutritional problems in the United States today is obesity, which results from the consumption of more calories than are expended. Consumption of fat is related to many disease states, such as heart disease. Successful reduction of fat consumption has not been achieved because of the dietary habits of the traditional American. Therefore, the search for fat substitutes or low-calorie fats has attracted attention in recent years.
Among the possible low-calorie fats or fat substitutes synthesized to date are sugar polyesters, polyglycerol esters, sucrose polyesters (SPE), neopentyl-type alcohols and other sugar derivatives such as sorbitol and mannitol, glycerol dialkyl ethers, triglyceride esters of alpha carboxylic acids, diglyceride esters of short-chain dibasic acids, trialkoxytricarballyate, polydextrose, palatinose, polygalactose, N-oil (tapioca dextrin), microbiologically derived products, nonabsorbable synthetic polymers with properties similar to edible oil, treederived products, low-metabolized natural fats and oils, biopolymers, branched polysaccharides and jojoba oil.
One method of reducing the caloric value of edible fats and retaining the characteristic functional physical properties of fats in foods is to prepare fatty acid esters of sugar or fatty acid esters of sugar alcohols that have reduced absorption and digestion. Absorption and digestion can be reduced by altering either the alcohol or fatty acid portion of the compound. In conventional synthesis procedures, for example, interesterification can be used to prepare sucrose polyesters. However, interesterification frequently requires high temperatures and toxic solvents such as dimethylacetamide, dimethylformamide, or dimethylsulfoxide. Therefore, conventional interesterification is not suitable for food applications.
Solvent-free, two-stage reaction sequences for making sucrose polyesters and avoiding the use of toxic solvents have been suggested. In the first stage, a 3:1 mole ratio of fatty acid methyl ester and sucrose is reacted in the presence of potassium soaps for forming a one-phase melt containing mainly esters of sucrose with a low degree of esterification. In the second stage, more methyl esters are added and reacted to produce a sucrose polyester in yields up to about 90% based on sucrose. This reaction is carried on the temperatures ranging from 130.degree. C. to 150.degree. C. It has been suggested that the sucrate ion generated with alkyl metal hydrides or sodium-potassium alloy catalyzes the sucrose polyester reactions. Modifications of this method have included adding methyl oleate at the beginning of the reaction and adding sucrose and sodium hydrides in increments. These modifications result in slightly different fatty acid composition and slightly lower degrees of esterification. About 80% to 90% yields of sucrose polyester have been achieved by reacting sucrose octaacetate and methyl palmitate in the presence of sodium or potassium at lower reaction temperatures, on the order of 110.degree. C. to 120.degree. C. In order to obtain 80% to 90% yields, however, the reaction must be continued for three to six hours.